Orthotics are generally considered to encompass any device that provides external biomechanic support to a human or animal body surface. For example, a foot orthotic generally takes the form of a partial or full insole for a shoe. An orthotic can include regions of support and/or relief for location between the skin/body of a subject and an environmental interface, e.g., a shoe sole. A region of support is generally designed to support weight-bearing regions of the subject and/or to provide correct positioning of a body region (e.g., the foot). A region of relief may be a softer, less-stiff region and is designed to off-load or distribute weight-bearing forces of specific regions of a subject's body so as to affect pressure in that local area, for instance to reduce pain and encourage wound healing. An orthotic may be used to support a region post-surgery, to improve gait of a user (in the case of a foot or leg orthotic), to provide relief from conditions such as ulcers, bony abnormalities, etc.
Foot ulcers affect up to 25% of all diabetics (estimated at over 25 million in the US as of 2015), and are a major national health concern given the growing diabetic population. Left untreated, foot ulcers can lead to loss of lower limb function and even amputation. In fact, approximately 85% of all lower limb amputations are preceded by a non-healing foot ulcer. Recent clinical research supports the use of orthotic shoe inserts to alter pressure conditions at foot ulcers. While traditional pressure-offloading foot orthotics can be effective in reducing ulceration and relieving pain, clinical prescription and design of these orthotics remains qualitative, and clinicians continue to struggle with accurate, effective, and repeatable methods to design foot orthotics that can affect pressure at the area of foot ulcers. Overall orthotic shape is usually satisfactory, but targeting of ulcer offloading accurately is geometrically and spatially imprecise, with correlation between the ulcer area and the offloading area often differing by 1 to 3 square centimeters (cm2). For example, FIG. 1 is a pressure heat map of a foot imprint showing a simulated area 1 of interest (e.g., a wound or ulcer) in the foot. In traditional orthotic formation, the offloading area, which ideally will encompass the area 1 as well as a portion of the surrounding area, will not take into account the pressure gradients and areas of the wound, leading to a qualitative prescription and the outcome of pressure reduction in the weight bearing regions including portions of the would itself.
In addition to design limitations, prolonged manufacturing times with existing fabrication methods reduce patient follow-up and compliance, thus impacting clinical outcomes. For instance, the current orthotic manufacturing cycle includes a shape capture of a region, e.g., a patient's foot, generally by taking an impression or a scan of the region, and the orthotic is then developed using manual techniques—optionally with the aid of software. The primary cushioning layer of a foot orthotic is generally fabricated from layering of multiple foam sheet materials followed by adhesion and vacuum forming over a model of the patient's anatomy, to create the custom shape of the orthotic with any additional base, cushioning or cover layers. Offloading regions may be machined as a recess in the sheet material and a less hard material positioned and attached in the recess. The entire process is time consuming (e.g., up to 2 weeks elapsed time), expensive (up to $250 per insert), off-site, inconsistent (difficult to recreate the same embodiment) and highly dependent on fabricator skill. Moreover, multiple office visits are often required due to multiple steps in the process and also adjustments for improper fit, particularly as the wound characteristics change over time, with few quantifiable metrics for assessment of effective offloading over time, leading to low patient compliance. In addition, the traditional fabrication method can lead to sharp boundaries between weight-bearing and offloading areas of the orthotic, which can further irritate wound areas and lead to increased pain, poor patient compliance, and slower healing.
What are needed in the art are improved orthotic materials and designs as well as a clinician-to-patient manufacturing cycle that can be utilized to produce the improved foot orthotics. For example, it would be useful to provide a custom-fit foot orthotic in reduced time through utilization of low cost, on-site manufacturing processes.